The letterTax · Income 2025, filing 2026
Adult child in France: prepare tax attachment versus deducted support
For income 2025, a French adult child may request tax attachment under age or study conditions; the parent accepts and includes their taxable income. Evidenced support may be deducted if the child is not attached to that same household and needs help, up to €6,855. These options cannot be combined. Prepare evidence and two tax simulations before signing: age alone does not identify the best option.
Julie by AlphaDeep is an AI legal assistant for French law: it researches official references to help answer your questions (Légifrance, case law, service-public), analyses your documents and drafts your letters, for individuals and professionals alike.
General legal information with official references and dated checks. It is not personalised advice: for a decision that commits you, have your situation checked by a qualified professional.
Let’s look at your situation
Prepare year, relevant age, studies, income and support evidence without tax identifiers.
Example questions
Your question carries over after signup. Maximum 400 characters. Avoid health data and names.
In which order should I prepare the tax choice ?
The choice concerns the same child and income year, not an abstract preference.
Check scope
Already adult on 1 January 2025, single without dependent children, outside disability cases for this tool. Other situations require separate review.
Prepare both scenarios
Attachment includes the child’s taxable income in the household. Separation uses their own return and evidenced support at the parent level.
Compare the total
Use the official simulator and add both taxes for separate returns. A deduction does not reduce tax by that same amount.
Sign and retain
Child’s written request, parent’s acceptance and supporting evidence. No support deduction by that same attached household.
Which options and evidence should I prepare for income 2025 ?
Fictional example: single child aged 22 on 1 January 2025, studying, family agreement, need and support established, housed for 12 months plus €3,000 other evidenced expenses. Prepared deductible support is capped at €6,855; the final choice needs two simulations.
Fictional example · the 2025 tax choice
Two scenarios to simulate: attachment without a support deduction, or separate returns with evidenced support. No tax winner is calculated.
- Attachment subject to agreement
- Age/study condition met within this scope
- Prepared housing/food allowance
- 4,075.00 €
- Prepared deductible support, income 2025
- 6,855.00 €
Demande sur papier libre, à signer par l’enfant et accepter par le parent ; conserver, ne pas envoyer automatiquement
[Nom et prénom de l’enfant majeur][Adresse de l’enfant]
[Nom et prénom du parent][Adresse du parent]
À [ville], le [date]
ObjetDemande de rattachement fiscal pour mes revenus de 2025
Je soussigné(e),
[nom, prénom, date de naissance], demande mon rattachement au foyer fiscal de [parent choisi] pour l’imposition de mes revenus de 2025.
Cette demande est un projet : je vérifierai les conditions et le choix fiscal avant de la signer. L’option est annuelle, irrévocable pour l’année et à exercer dans le délai de déclaration ; ce projet n’autorise pas une option tardive. Le parent doit accepter le rattachement et inclure les revenus imposables concernés dans sa déclaration.
Pour le même enfant et la même année, ce foyer ne peut pas cumuler rattachement et déduction d’une pension alimentaire.
Acceptation du parent : [nom, date et signature du parent].
Je conserve cette demande avec les justificatifs utiles.[Signature de l’enfant majeur]
Pièces jointes : justificatif d’âge ; preuve d’études à la date pertinente en 2025 ; liste des revenus imposables de 2025 à intégrer
Income 2025 only: €6,855 cap, €4,075 annual allowance. Attachment is an annual option, irrevocable for that year and exercised within the filing deadline; this draft does not validate a late option. The recipient reports deducted support. Compare the sum of tax on the two separate returns with the attached household in the official simulator. Check student-wage exemptions, benefits and foreign income. DGFiP simulators.
Which age and study conditions allow attachment ?
Ordinary attachment covers someone under 21 on 1 January 2025, or under 25 pursuing studies. Keep study evidence for 1 January or 31 December as relevant. Disabled children, a child with their own household and adulthood reached during 2025 have distinct rules: this tool does not decide them.
Sources: CGI, article 6 : option de rattachement · DGFiP: adult children on 1 January · DGFiP : demande de rattachement
What evidence supports a support deduction ?
The child must need the help, and the amount must suit the parent’s means. Keep actual payments made to or for them and evidence of need. Age or student status alone is insufficient. The child or household receiving their attachment reports deducted support. Contact-visit costs cannot be deducted as support.
Sources: CGI, article 156 II 2° : version from 21 February to 1 July 2026 · DGFiP: support for adult children, 2025 income
How can I use the housing allowance without double counting ?
For income 2025, the annual housing and food allowance is €4,075 when the child lives with you and has insufficient resources. Prorate to the months concerned, counting every started month. Other evidenced costs may supplement support within the €6,855 cap, without counting housing and food again.
How should I compare without promising the lowest tax ?
Simulate the attached household including the child’s taxable income. Then simulate the parent with accepted support and the child separately with received support. Compare total tax and check student exemptions and impacts on other benefits. The document does not calculate income tax, amend a filed return or replace the annual option.
Sources: DGFiP: adult children on 1 January · DGFiP: support for adult children, 2025 income · DGFiP : demande de rattachement
Which elements change between the scenarios ?
| Element | Attachment | Separate returns |
|---|---|---|
| Child’s income | Include under its applicable tax rules | Child reports under applicable rules |
| Support at this parent’s level | No deduction for the attached child | Conditional evidenced support |
| Ordinary support cap | Not applicable | €6,855 |
| Annual housing/food allowance | No combined deduction | €4,075, prorated to started months |
| Document to keep | Signed and accepted request | Evidence of need and support |
Married children, civil partners or those with dependent children use a different allowance rather than the same tax shares. That case and income-year 2026 amounts are not calculated here.
Sources: CGI, article 6 : option de rattachement · CGI, article 196 B : abattement 2025 · CGI, article 156 II 2° : version from 21 February to 1 July 2026 · DGFiP: adult children on 1 January · DGFiP: support for adult children, 2025 income
Why can these two options not be combined ?
No-combination rule, confirmed by article 156 versions and the DGFiP income-2025 guides.
Un contribuable ne peut, au titre d'une même année et pour un même enfant, bénéficier à la fois de la déduction d'une pension alimentaire et du rattachement.
In English, briefly (our summary, not an official translation): The prohibition concerns the same income year and child for the household concerned. Another parent may have a different position; evidence and the recipient’s income still need examination.
What should I settle before signing ?
Is attachment automatic after adulthood ?
No. The option requires the child and parent to agree; it is annual, irrevocable for that year and exercised within the filing deadline. It must be renewed for another year. Relevant taxable income enters the household.
Can a child attach to both separated parents ?
No: attachment belongs to one household. The year of adulthood needs specific review.
Does €6,855 support reduce tax by €6,855 ?
No. It is a conditional income deduction, not a same-sized tax reduction. Compare complete simulation results.
Can I reuse these amounts for income 2026 ?
No. The tool explicitly uses income 2025, filing 2026. Another income year blocks the amount and requires fresh verification.
Which official laws and guides should I check ?
- CGI, article 6 : option de rattachementLégifrance
- CGI, article 196 B : abattement 2025Légifrance
- CGI, article 156 II 2° : version from 21 February to 1 July 2026Légifrance
- DGFiP: adult children on 1 JanuaryDGFiP
- DGFiP: support for adult children, 2025 incomeDGFiP
- DGFiP : demande de rattachementDGFiP
- CGI, article 156 : version from 1 July 2026Légifrance
Texts cited last checked: 30 September 2026